SE, just saw your OP, I don't regularly frequent this neck of the woods, though I did more often wearing my other, more snarky avatar.
I've seen the same kind of thing and just recently as well. Not all local families do this but every time I have seen it it was from local families .
Well, yours was a timely post, as just last Friday there was a big article in that rag the ST, which I only read because it was a courtesy copy in the doctor's office...
...about how maids are now becoming picky - the title of the article was something like "Expats only".
According to the article, seems the Philippinas are no longer putting up with poor treatment from local host families, because they get better treatment, more days off, etc. from foreigner hosts, so they are turning down offers from local families. Or so the article says.
It was just a matter of time.